Written By Steven Craig
ARTIST PROFILE
STEVEN CRAIG
DATA
Steven Craig is the owner and head painter of SKC CUSTOMZ in Lake Havasu City, AZ. In the past Steven has won the House of Kolor Prestigeous Painter Award and was a 1st Place winner of Dupont's Hot Hues Awards. He most recently was awarded the Matrix System's FX Grand Prize Award. Steve paints a wide range
of jobs from guitars to large off shore boats. Visit his web site at
Airbrush
:
Iwata HP-BH, Custom Micron B
Spray Guns:
Iwata LPH400 ,Iwata LPH300, Iwata LPH-80
Paint Media:
PPG, Xotic Colours, Dupont and Matrix Systems
Surface Media:
Everything I can get paint to stick to.
Masking
:
R-Tape and 3M Masking Tapes
Projector:
Artograph
Lighting
: Natural and Florescent. Spray-Line and Spray King Paint Booths
"Body Work Basics"
Hand-made sheet metal for custom motorcycles are notorious for their imperfections. It usually takes a great deal of bodywork to get the metal straight before painting. The above photo is a perfect example of rough sheet metal and will make an excellent subject for this article. Highlighted by the red circles, you can see uneven surface areas, deep indentations and raised welds.
This first step is where many people start off wrong right from the beginning. I've repaired many jobs that were done by another shop and found the prep work was no more than a light scuffing of the substrate. To ensure good adhesion, raw metal should be aggressively sanded with no less than 80 grit sandpaper. This photo illustrates the deep cut pattern created by the sandpaper, using a DA (Air driven orbital sander made specifically for bodywork).
Don't use sandpaper that is larger than 80 grit. Anything courser will create deep gouges in the metal and could resurface months after the project was completed. This happens when material cures and does what is called "Shrink-Back", where the material tightens up as it cures. After thoroughly sanding, inspect the substrate for "Low-Spots". Low spots are small imperfections in the substrate that are lower than the overall surface. This is highlighted in the red circled area above.
Fillers will not bond to areas that have not opened up by sanding. The untreated areas of hardened steel contain oils and other contaminants. This creates a barrier and there is nothing for the filler or primer to adhere to. If this is overlooked these areas may cause problems such as fillers breaking loose and paint lifting. Take a angle grinder with an 80 grit sanding disk and taper the metal away from the imperfection until the metal is level to the indentation. Click here for more information on feathering damaged areas.
Bare metals contain oils. These contaminants need to be removed before proceeding. There are several metal conditioners on the market that can be used. I prefer loading up a spray gun with Lacquer Thinner and spraying the surface with the spray pattern cocked down to a high pressure stream. This will lift the oils and push them off the substrate. When doing this, you will see the fluid turn black as it moves off the surface. This is oils being released and lifted from the surface. Contrary to what some people may advise, do not wash the metal off with soap and water. Moisture will start to create rust within minutes.
Wipe off the lacquer thinner before it evaporates. If it dries on the surface all that was accomplished was moving the contaminants to a different area. To ensure that all the oils have been removed, wipe down the surface again using a wax and grease remover.
Mix the recommended ratio of body filler and hardener. Do not add too much hardener, you don't want the filler to get hard to fast. You will want to be able to work with it as it goes through the curing process. Use a plastic spreader a thoroughly mix together with a "folding" motion that is similar to mixing cake batter. The filler is completely mixed when there are not signs of any color variations. If this is not done correctly, there will be spots where the filler will never cure and can create air bubbles.
Above is another photograph showing how uneven the sheet metal is. You will notice that in the center of the tank, just below the filler tube, the sheet metal dips inwards. At the top edges of the sides there is a bead weld that is raised higher than the overall surface. These welds cannot be ground down because the metal may become to thin and cause a structural weakness where the welds could crack. To obtain a level surface, the entire top will require a "Skim-Coat" of filler.
If the surface is extremely uneven, apply an excessive amount of filler. You want to have enough thickness to be able to level or reshape the surface. Have enough filler made to cover the entire surface. If you do not have enough filler made to completely cover the repair area, do not make up another batch and try to overlay it with the already curing first application. By doing so, you risk that the two separate applications will not adhere to each other. If this happens, let the first application cure and sand with 80 grit sandpaper to reopen the the filler to accept and adhere to the next application of filler.
Only use premium fillers. Inexpensive fillers will cause nothing but grief and are very hard to work with. When applying over bare metal a filler must be used that is designed for that specific substrate. Evercoat's Z-Grip has superior adhesion properties for galvanized steel, bare steel and aluminum. The tools needed for the following step are: Filler, a clean board for mixing, a spreader and a rasp which is also referred to as a "Cheese-Grater".
To do a "Skim-Coat" start at a leading edge and apply the body filler with a plastic spreader. Firmly press down as the filler is spread across the substrate to force out any air pockets. Apply thin coats to restore the contour of the surface. When applying body filler, try to maintain 1/8" of filler and not to exceed more than 1/4". Applying too much filler can lead to cracking.
To begin the shaping process you need to know exactly when to begin shaping. This has to be done before the filler is completely cured and not too early when it is still wet. You can usually tell when its time by touching the filler to check for firmness. You can also tell when it is beginning to flash (harden) when the material feels hot to the touch.
Start shaping by holding the rasp with both hands and firmly place against the surface. Begin at a leading edge where bare metal is exposed. You can use the bare metal as a guidline and reference point when shaping the filler.
Many of these steps are almost impossible to do a "text book" tutorial on. They take practice and are achieved through experience but I'm going to do my best to explain them so you may have a understanding of the process. The filler needs to be in a soft and workable stage. This is usually about five minutes before it begins to cure and gets hard. Start at the top and at a leading edge and work the rasp in a diagonal pattern. Make complete strokes from one side to the other. Once an entire pass has been done, start at the top of the opposite side and repeat the process with a diagonal cut creating a criss-cross (X) pattern. They call the rasp a cheese grater because it is virtually like grating a chunk of cheese. This should be able to be accomplished with very little force being applied to the filler. If the filler has become hard and you are having to applying forceful pressure to remove the filler, STOP! This will create huge valleys in the filler. If this happens, sand the filler with 80 grit paper, apply a new coat of filler and start again.
(Step #13 continued) Once you've completed the criss-cross pattern, run your hand over the surface. If you have a light enough touch you will be able to feel high spots. Use the rasp to shape these high spots and level them with the surface. On extremely uneven surfaces this process may need to be done more than once. If that is the case, sand the surface with 36 grit paper, blow off the surface with an air hose to remove loose debris and repeat step 13. Once you are confident that the shaping of the filler is level your ready to move on. Be prepared, we are going to do a lot of sanding from this point on. Above you will see a photo of the three types of sanding blocks I use. These are available from 3M and each one has its specific use. The "Long-Board" is for large panels. I use this mainly for car restorations. The smaller of the three is made of a foam composite and even though it has a flat bottom for blocking a surface flat, it is capable of flexing to level curved areas.
The shaping and leveling process continues... The size of the area being leveled dictates which sanding block is used. Motorcycle parts are short in length and have many curved in the surface. For the next step I'm going to use the short soft block. I prefer the "Hook-It" system for sanding. One reason is that when the sandpaper begins to clog you can simply peel the sandpaper off the block and it removes all the filler material. This helps make the sandpaper last much longer. The rasp leaves deep cuts in the filler which need to be removed. The deep grooves are acceptable because they can be used as a guide in the level process.
By observing the change in color of the filler, the dark color variance depicts a low spot in the surface. If it is minor there is no need to add any filler at this point. Most of these will be eliminated through the continued leveling process. In many cases the low spots can be removed by continuing to shape the filler with the rasp. If there is a major indentation, add more filler to that area and bring it back down level with the rasp to the previous application of body filler.
Start by sanding with course 36 grit paper. Never start from the inside of the area containing filler. Always begin at a leading edge so you can use the bare metal of the substrate as a guide. Sand diagonally in the opposite direction of the groove created by the rasp. Constantly change directions with the sanding block but maintaing diagonal cut patterns. You should avoid going over an area in the same direction as the previous step. Doing so will cause an uneven surface.
Continue sanding until all the grooves created by the rasp are no longer visible. If there are any low spots remaining, do not try to get rid of them by continuously sanding in that specific area. Once again, that will do nothing but make the low spot even larger. For now, just concentrate on achieving the desired shape of the surface area. Further steps to level the surface is yet to come.
More experienced technicians use an Air-file to speed up the process. I would not recommend using an Air-file if you are just learning body work. When first learning to do body work do it by hand. This will help you develop the feel for creating flat finishes.
Getting Rough Sheet Metal
Ready For Paint
In the world of Custom Paint there is more to it than just being a great artist. The artwork is the easy part but will lose all of its appeal if the surface below it is not perfectly flat and the top coat is not a pristine smooth glass finish. This tutorial will help guide you to achieve a perfect canvas. I will show you how to take raw sheet metal for a custom motorcycle and prepare it for paint. When it comes to doing bodywork there are as many ways to do the process as there are products to achieve it. This project is going to be reshaped and leveled by using nothing more hand fillers and primers. This is a basic guide to bodywork. More extensive preparation would include several other materials and possibly welding and straightening with body shop tools.
You can check the radius of curved surfaces by laying a straight edge or ruler on top of the substrate. Walk the straight edge down the substrate and look for high and low spots. Now is the time you add or remove filler before continuing.
